There have been image forming systems which communicably connect an image forming apparatus and a data processor and comprises a secure print function. When utilizing this secure print function, a user makes a print request, with an unlocking condition (for example, a password) designated on a data processor. And then, in the image forming apparatus side, a print job based on the print request is registered as a locked job, and the print processing of the locked jog is prohibited until the above unlocking condition is fulfilled (for example, until the same password as the above password is input in the image forming apparatus). When the unlocking condition is fulfilled, other configurations wait for the end of print processing if it is in the middle of print processing of other print job, before conducting print processing of a locked job (hereinafter referred to as “conventional configuration A”), or cancels print processing if it is in the middle of the print processing of other print job, before conducting print processing of a locked job (hereinafter referred to as “conventional configuration B”).